1. Field of the Invention
The present invention relates to an air bag system equipped in vehicles such as an automobile.
2. Description of the Related Art
In order to protect an occupant at a time of a side impact time of an automobile and prevent an occupant from being thrown out of the automobile at a time of a roll over thereof, an automobile equipped with a so-called curtain air bag has been known. A curtain air bag of this kind has been disclosed, for example, in Jpn Pat. Appln. KOKAI Publication No. 2001-260806.
An occupant-protective device disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2001-260806 has two functions. One of the functions is to actuate both a curtain air bag and a seat pretensioner at a time of an urgent roll over at which an absolute value of a roll velocity of a vehicle body is large, and the other thereof is to make the curtain air bag inoperative and actuate only the seat pretensioner at a time of a calm roll over at which the absolute value of the roll velocity is small. In a vehicle equipped with such a curtain air bag, it is desired to suppress an internal pressure of the curtain air bag to a low value in order to properly protect the head of an occupant at the time of the side impact time of the vehicle.
However, when the internal pressure in the curtain air bag is low at the time of the roll over, a shape-holding power of the curtain air bag lowers. For this reason, when a window on a lateral area of a vehicle body is opened or a window glass breaks, a performance for holding an occupant inside the vehicle being rolling may lower.